寒假刷题13： Anu Has a Function Codeforces Round #618 (Div. 2) C

题目链接：
Anu Has a Function

题目解析：
观察函数f(x,y)定义:(x|y)-y
即 取出来x里是1但是y里不是1的地方 也就是 x&(~y)
（也可以列真值表）
因此题目就变为求 a1&(∼a2)&…(∼an) 最大值
先预处理出前缀按位和以及后缀按位和，再求出最大值即可

AC代码：

#include<iostream>
#include<cstdio>
#include<cstring>
#include<map>
#include<algorithm>
#include<cmath>
#include<vector>
using namespace std;
#define ll long long
int a[100010],prefix[100010],suffix[100010],n;
int main()
{scanf("%d",&n);for(int i=1;i<=n;i++){scanf("%d",&a[i]);if(i==1) prefix[i]=(~a[i]);else prefix[i]=(~a[i])&prefix[i-1];}suffix[n]=~a[n];for(int i=n-1;i>=1;i--) suffix[i]=(~a[i])&suffix[i+1];//for(int i=1;i<=n;i++) printf("%d\n",prefix[i]);int maxx=-1,id;for(int i=1;i<=n;i++){int temp=(prefix[i-1]&suffix[i+1]&a[i]);if(i==1) temp=(a[1]&suffix[2]);if(i==n) temp=(a[n]&prefix[n-1]);if(temp>=maxx) {maxx=max(maxx,temp);id=i;}}printf("%d ",a[id]);for(int i=1;i<=n;i++)if(i!=id) printf("%d ",a[i]);
}

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